There are two ways of writing the argument to typeof: with an expression, or with a type. The following is an example with an expression.
typeof (x[0](1))This input assumes that x is an array of functions; the type described is that of the values of the functions. The following is an example with a type name as the argument.
typeof (int *)If you are writing a header file that must work when included in ANSI C programs, write __typeof__ instead of typeof. See Alternate keywords. A typeof-construct can be used anywhere a typedef name could be used. For example, you can use it in a declaration, in a cast, or inside of sizeof or typeof. In the following, the type described is that of pointers to int.
typeof (*x) y;
typeof (*x) y[4];
typeof (typeof (char *)[4]) y;It is equivalent to the traditional C declaration, char *y[4];.
To see the meaning of the declaration using typeof, and why it might be a useful way to write, lets rewrite it with the following macros.
#define pointer(T) typeof(T *) #define array(T, N) typeof(T [N])Now the declaration can be rewritten the following way.
array (pointer (char), 4) y;Thus, array (pointer (char), 4) is the type of arrays of 4 pointers to char.